1. Field of the Invention
The present invention relates to an endoscopic treatment instrument such as a diathermic cutter for performing a resection treatment of resecting a living tissue.
2. Description of the Related Art
Conventionally, a treatment for resecting a living tissue, such as a mucous membrane, has been performed using an endoscopic treatment instrument, which is inserted into the body, for example, through the channel of an endoscope. In the treatment of resection, a diathermic (high-frequency) treatment instrument as disclosed, e.g. in Jpn. Pat. Appln. KOKAI Publication No. 62-50610 (Patent Document 1), is used.
The diathermic treatment instrument disclosed in Patent Document 1 has an elongated insertion section to be inserted in the channel of an endoscope, and an axially extending needle-like cutter section (electrode section) provided at a distal end portion of the elongated insertion section. In use, a high-frequency current is supplied to the cutter section. Thereby, a living tissue put in contact with the cutter section is cauterized and cut.
Jpn. Pat. Appln. KOKAI Publication No. 8-299355 (Patent Document 2) discloses a diathermic treatment instrument different from that of Patent Document 1. This diathermic treatment instrument has a ball-shaped electrical insulator at a distal end of the needle-like cutter section (electrode section).
Other diathermic treatment instruments with different structures are disclosed in Jpn. U. M. Appln. KOKAI Publication No. 60-184513 (Patent Document 3) and Tsuneo OYAMA et al. (six others), “Endoscopic Mucosal Resection Using a Hocking Knife”, Stomach and Intestines, Aug. 2002, Vol. 37, No. 9, pp. 1155-1161 (Non-Patent Document 1). In these techniques, a bent portion to be hooked on a living tissue is provided at a distal end of the cutter section (electrode section), and while the living tissue hooked by the bent portion is being pulled up, it is cauterized and cut.
Jpn. Pat. Appln. KOKAI Publication No. 5-293118 (Patent Document 4) and Jpn. Pat. Appln. KOKAI Publication No. 8-126648 (Patent Document 5) disclose diathermic treatment instruments each having an outer tube and an insertion member to be inserted in the outer tube. A treatment section is provided at a distal end portion of the insertion member. A proximal-side portion of the insertion member to be inserted in the outer tube is rotated about its axis, whereby the entire insertion member is rotated about its axis. Thus, the rotation of the insertion member is transmitted to the distal-side treatment section, and the direction of the distal-side treatment section is changed.
The following operation is performed in resecting a living tissue using the diathermic treatment instrument disclosed in Patent Document 1. To start with, a to-be-resected part is punctured with a cutting section. The cutter section is then moved in a predetermined direction of resection. In many cases, the to-be-resected part is located on the surface side of the living tissue, and a tissue that is not to be resected is present in a deep region of the to-be-resected part. The surgeon is required to resect only the to-be-resected part. Therefore, the cutter section needs to be moved in the state in which the cutter section inserted in the to-be-resected part is kept at a constant depth. This prevents the cutter section, which is inserted in the to-be-resected part, from contacting the non-to-be-resected tissue located at a deep region of the to-be-resected part (i.e. from applying an electric effect on the non-to-be-resected tissue).